In an oil field it is known to pump sand by way of a fluid (frac) into the ground in an oil well stimulation or fracturing process. The material is forced by pressure through a frac line by a primary pumper, i.e. the source where fluids, sand and chemicals are mixed or blended together, and it is desirable to know, but difficult to determine, the final destination of the material underground. To do this, a tracer element in minute quantities has been added to the frac material, i.e. a radioactive tracer element. There has not, however, been any means of providing a consistent concentration of the radioactive material relative to the frac material and, obviously, such lack of control makes it difficult to determine with any accurcy the final distribution and destination of the frac material underground.
The prior art procedure for adding the radio-active material consisted of having an individual pour, from a bottle using long handled tongs, radioactive sand into the fluid or sand before entering a mixer where the fluid and sand is mixed. This is not only dangerous for the one handling the material but also it fails to provide any degree whatsoever in the consistency of concentration. The amount of radioactive material per tonne of sand demanded varies from one customer to another and the common range is from 1 to 3 millicurries of radioactive material per tonne of sand. The sand is added to fluids being pumped. Determining what rate the sand is being added to the fluids being pumped is done by multiplying the rate per minute by the sand concentration, for example: EQU 100 kg/m.sup.3 .times.3 m.sup.3 /min=300 kg/min or 0.3 tonne.
Some frac companies call for their fracs in the standard measuring system which, for example may be 3 lbs/gal and 18 barrels/min. From this it will be realized a very minute quantity of radioactive material is being added. The prior system used has a number of deficiencies which are quite severe and the most obvious are as follows:
(a) The bottle of material used by the individual is not all radioactive material. About 90-95% of the contents is filler so that the material can be poured slowly enough. This does not allow for a totally accurate trace as the radioactive material is not added consistently. PA1 (b) Radioactive material is added with only an estimated accuracy as it is impossible to know how much actual radioactive material is being added with the filler and there is no way of accurately controlling how fast or slow the material is being added. PA1 (c) Radioactive particles may become air-borne when being poured in windy conditions. PA1 (d) Equipment being used has the possibility of becoming contaminated as the radioactive material passes through all the equipment (mixer and pumper) used for the job. PA1 (e) Exposure to radioactive energy is much higher as there is no lead shielding incorporated and the length of time spent with the material can be quite extended. Where the material is being added there are always 2 to 6 workers subject to exposure. PA1 (f) The location of personnel injecting the radioactive material is considered dangerous. Most disasters usually happen at the piece of equipment where the individual adding the radioactive material must be located. PA1 (g) Contamination due to spillage is possible as once the cap of the bottle has been removed the contents are loose and can be spilled very easily. PA1 (a) determining the flow rate of said stream of material; PA1 (b) metering a filler material having a known minor quantity of radioactive material evently distributed therethrough at a rate dependent upon said flow rate to provide the desired concentration of radioactive material in the flowing material; and PA1 (c) injecting said filler having the radioactive material therein during metering thereof directly into the flowing stream at a location downstream from the source causing said stream to flow. PA1 (a) a lead shielded chamber for holding a supply of filler material having a radioactive tracer element evenly distributed therethrough; PA1 (b) means for progressively decreasing the volume of said chamber at a predetermined rate to meter outflow of the filler material with the radioactive tracer therein from said chamber; and PA1 (c) means for feeding the metered material into a line carrying the frac material.